I have been having issues with rough idle on startup but then levels out but while driving once it get into overdrive it start back running rough , skipping and jerking , i have put new plugs and wires on it and also cleaned the mass air flow sensor , any other thoughts on what i need to do to fix the issue ? It dont do it all the time sometimes it will level itself out and stop the skipping and jerking and i notice its worst it i let the truck sit for 2 or 3 days before i drive it. , if i drive it every day it dont seem to do it as much. , any idea on what i need to do to stop the skipping and jerking?
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There is a vacuum modulator valve on the automatic transmission that is known to leak. Engine vacuum powers the modulator, and when it fails, your engine can start sucking transmission fluid into the intake system. Sometimes you can find reddish oil in your throttle body. The modulator is used to kick down the transmission to a lower gear when you step on the gas (engine vacuum drops), so now not only can oil in the air intake make your engine run poorly, a failing modulator can play havoc with your auto trans. Good news is the part is less than $20 and pretty easy to replace. Can't post a link yet (low post count), but search for "FRAM 2336 Transmission Modulator" on Amazon. Check fitment, because there are a couple models of auto trannys used on this model. Recommend you replace the vacuum line to this while you're at it. Something more painful would be a small coolant leak due to a failing head gasket that is just enough to make it run crappy when starting, but not enough to blow steam out the exhaust. Compression check would pick that up.
